shithub: libvpx

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Merge "Disallow skipping transform and quantization" into main

--- a/vp9/encoder/vp9_block.h

+++ b/vp9/encoder/vp9_block.h

@@ -157,6 +157,9 @@

   // skip forward transform and quantization

   uint8_t skip_txfm[MAX_MB_PLANE << 2];

 #define SKIP_TXFM_NONE 0

+// TODO(chengchen): consider remove SKIP_TXFM_AC_DC from vp9 completely

+// since it increases risks of bad perceptual quality.

+// https://crbug.com/webm/1729

 #define SKIP_TXFM_AC_DC 1

 #define SKIP_TXFM_AC_ONLY 2

--- a/vp9/encoder/vp9_rdopt.c

+++ b/vp9/encoder/vp9_rdopt.c

@@ -745,8 +745,8 @@

   MODE_INFO *const mi = xd->mi[0];

   int64_t rd1, rd2, rd;

   int rate;

-  int64_t dist;

-  int64_t sse;

+  int64_t dist = INT64_MAX;

+  int64_t sse = INT64_MAX;

   const int coeff_ctx =

       combine_entropy_contexts(args->t_left[blk_row], args->t_above[blk_col]);

   struct buf_2d *recon = args->this_recon;

@@ -799,6 +799,13 @@

     if (max_txsize_lookup[plane_bsize] == tx_size)

       skip_txfm_flag = x->skip_txfm[(plane << 2) + (block >> (tx_size << 1))];

+    // This reduces the risk of bad perceptual quality due to bad prediction.

+    // We always force the encoder to perform transform and quantization.

+    if (!args->cpi->sf.allow_skip_txfm_ac_dc &&

+        skip_txfm_flag == SKIP_TXFM_AC_DC) {

+      skip_txfm_flag = SKIP_TXFM_NONE;

+    }

+

     if (skip_txfm_flag == SKIP_TXFM_NONE ||

         (recon && skip_txfm_flag == SKIP_TXFM_AC_ONLY)) {

       // full forward transform and quantization

@@ -827,17 +834,7 @@

         dist = VPXMAX(0, sse - dc_correct);

       }

     } else {

-      // SKIP_TXFM_AC_DC

-      // skip forward transform. Because this is handled here, the quantization

-      // does not need to do it.

-      x->plane[plane].eobs[block] = 0;

-      sse = x->bsse[(plane << 2) + (block >> (tx_size << 1))] << 4;

-      dist = sse;

-      if (recon) {

-        uint8_t *rec_ptr = &recon->buf[4 * (blk_row * recon->stride + blk_col)];

-        copy_block_visible(xd, pd, dst, dst_stride, rec_ptr, recon->stride,

-                           blk_row, blk_col, plane_bsize, tx_bsize);

-      }

+      assert(0 && "allow_skip_txfm_ac_dc does not allow SKIP_TXFM_AC_DC.");

     }

   }

--- a/vp9/encoder/vp9_speed_features.c

+++ b/vp9/encoder/vp9_speed_features.c

@@ -940,6 +940,7 @@

   sf->enable_tpl_model = oxcf->enable_tpl_model;

   sf->prune_ref_frame_for_rect_partitions = 0;

   sf->temporal_filter_search_method = MESH;

+  sf->allow_skip_txfm_ac_dc = 0;

   for (i = 0; i < TX_SIZES; i++) {

     sf->intra_y_mode_mask[i] = INTRA_ALL;

--- a/vp9/encoder/vp9_speed_features.h

+++ b/vp9/encoder/vp9_speed_features.h

@@ -612,6 +612,12 @@

   // For real-time mode: force DC only under intra search when content

   // does not have high souce SAD.

   int rt_intra_dc_only_low_content;

+

+  // The encoder has a feature that skips forward transform and quantization

+  // based on a model rd estimation to reduce encoding time.

+  // However, this feature is dangerous since it could lead to bad perceptual

+  // quality. This flag is added to guard the feature.

+  int allow_skip_txfm_ac_dc;

 } SPEED_FEATURES;

 struct VP9_COMP;